This invention relates to an apparatus for separating opened fiber tufts from an air stream for the purpose of, for example, supplying the fiber tufts to a fiber processing machine such as a carding machine, a cleaner or the like. The apparatus has a feed chute communicating with a fiber tuft transporting duct from which the feed chute is charged with the fiber tufts. At the lower end of the feed chute a delivery device is arranged which withdraws the fiber tufts from the feed chute and discharges them in the form of a fiber lap. There is further provided an air-pervious partition (screen) for separating the fiber tufts from the air stream and for guiding the air stream out of the feed chute. The screen is adjoined externally of the feed chute by an air removal chamber which has an air inlet opening through which the air stream enters the air removal chamber and further, the air removal chamber is adjoined by an air removal conduit.
German Offenlegungsschrift (application published without examination) 35 04 607 discloses a fiber tuft feeder for a card. The feeder has an upper chute (reserve chute) and a lower chute (feed chute) adjoining the upper chute. The feed chute has an upper, open inlet end and a lower, open outlet end. At the inlet end of the feed chute a fiber tuft advancing device is arranged which includes a feed roller and an opening roller. Underneath the outlet end of the feed chute two delivery rollers are situated which withdraw the fiber tufts from the feed chute and advance them, as a fiber lap, to the fiber processing (carding) machine. Further, air guiding elements are provided which form a closed air circulation system and which serve for maintaining an air stream in the feed chute, oriented in the direction of the outlet end thereof. The air guiding elements include air outlet openings (constituting a screen) which are arranged in the feed chute between the inlet and the outlet ends in the chute wall. An air duct positioned externally of the feed chute has a first open end oriented towards air removal chambers adjoining the screen or screens and a second open end oriented towards the inlet end of the feed chute. In the duct a fan is positioned to drive air in a closed path into the inlet end of the feed chute, out of the feed chute through the air outlet openings and through the air removal chambers into the air duct. Above the reserve chute a fiber tuft transporting conduit is arranged for the pneumatic transport of the fiber tuft from an upstream-arranged fine opener to serve the reserve chutes of a plurality of tuft feeders. Inside the air duct between the fan and the inlet end of the feed chute an air distributing device is arranged for uniformly distributing air over the duct width. In the lower region of the feed chute two comb-shaped screens are arranged which function as separating walls. The vertical tines of the screens are spaced from one another by vertical slots which have a width of approximately 2.5-5 mm. Such a width is less than the expected minimum size of the fiber tufts to be separated from the air stream. Each screen is adjoined by a box-like air removal chamber which has a rectangular cross-sectional outline and which, over its width, has an air inlet opening which is oriented towards a planar wall of the chamber at a distance therefrom. The bottom and ceiling walls of the chamber are also planar. The air exits from the feed chute perpendicularly to the screens and enters the respective air removal chambers. At one of their front faces the box-like air removal chambers are connected with one another by a coupling channel extending externally of the lateral wall of the feed chute. The air removal duct communicates with the chambers at those front faces.
It is a disadvantage of the air removal chamber of conventional construction that it has corners in the flow path and a relatively large cross-sectional area. As a result, the flow velocity in the chamber is relatively small so that in the corners heavy parts (trash) may be deposited which capture fibers and may lead to obstructions. It is a further drawback that at low air speeds sticky substances usually present in cotton may adhere to the inner chamber walls. It is also a drawback that the large cross-sectional inner chamber area causes a pressure loss which leads to the requirement of a high energy input for the air removal. It is also a disadvantage that the corners of the box-like chamber may cause air turbulences which adversely affect an aerodynamically favorable removal of the air. Also, the box-like air removal chambers require a substantial technical and constructional outlay.